What is the recommended dosage of apixaban (Elequis) for a 78-year-old patient with atrial fibrillation (aFib), weighing 70 kg, and impaired renal function (creatinine level 1.62 mg/dL)?

Apixaban Dosing Recommendation

This patient should receive apixaban 5 mg twice daily, as they meet only ONE of the three dose-reduction criteria (age ≥80 years, weight ≤60 kg, or serum creatinine ≥1.5 mg/dL), and dose reduction to 2.5 mg twice daily requires at least TWO criteria to be met. 1, 2

Dose-Reduction Criteria Assessment

Let me walk through the systematic evaluation of this 78-year-old patient:

Criteria Analysis:

• Age: 78 years (does NOT meet the ≥80 years threshold) 1, 2
• Weight: 70 kg (does NOT meet the ≤60 kg threshold) 1, 2
• Serum Creatinine: 1.62 mg/dL (MEETS the ≥1.5 mg/dL threshold) 1, 2

Since only 1 of 3 criteria is met, the standard dose of 5 mg twice daily is appropriate. 1, 2

Renal Function Considerations

The serum creatinine of 1.62 mg/dL alone does not trigger dose reduction, despite being above the 1.5 mg/dL threshold. 1 Here's why this approach is evidence-based:

• Apixaban has only 27% renal clearance, making it the safest direct oral anticoagulant in renal impairment compared to dabigatran (80% renal) or rivaroxaban (66% renal) 3, 1
• The ARISTOTLE trial demonstrated that patients receiving standard 5 mg twice daily dosing with only one dose-reduction criterion had similar efficacy and safety profiles compared to warfarin 1
• Moderate renal impairment (CrCl 30-59 mL/min) alone does not mandate dose reduction unless combined with other criteria 1, 4

Calculate creatinine clearance using the Cockcroft-Gault equation to fully assess renal function, as this is what FDA labeling and clinical trials used for dosing decisions. 1

Critical Pitfall to Avoid

The most common prescribing error with apixaban is inappropriate dose reduction based on a single criterion rather than requiring two. 1 Studies show that 9.4-40.4% of apixaban prescriptions involve underdosing, often driven by clinician concern about renal function or perceived bleeding risk when formal criteria are not met. 1

Do not reduce the dose based solely on:

• Perceived bleeding risk without meeting formal criteria 1
• A single dose-reduction criterion 1, 5
• eGFR values alone (use Cockcroft-Gault CrCl instead) 1

Monitoring Requirements

Given the elevated creatinine, implement the following monitoring strategy:

• Reassess renal function every 3-6 months given the creatinine >1.5 mg/dL and potential for declining function 1
• Studies show 29% of patients with heart failure or CKD require apixaban dose adjustments during follow-up due to changing renal parameters 1, 6
• If CrCl declines to <30 mL/min, consider dose reduction to 2.5 mg twice daily with caution, or switch to warfarin 1
• Monitor for bleeding symptoms, particularly gastrointestinal, in elderly patients 1

Drug Interactions to Avoid

Contraindicated or cautionary medications include:

• Strong P-glycoprotein and CYP3A4 inhibitors (ketoconazole, ritonavir, verapamil) - may require dose reduction to 2.5 mg twice daily 1, 4
• Strong CYP3A4 inducers (rifampin, St. John's wort) - avoid use 1, 4
• NSAIDs and COX-2 inhibitors - can worsen renal function and increase bleeding risk 4

When Dose Reduction Would Be Appropriate

This patient would require dose reduction to 2.5 mg twice daily if they develop any ONE of the following additional criteria:

• Age reaches ≥80 years (in 2 years) 1, 2
• Weight decreases to ≤60 kg 1, 2
• Develops a strong P-glycoprotein/CYP3A4 inhibitor requirement 1

The dose should NOT be doubled if a dose is missed; simply take the next scheduled dose. 7